Philadelphia turned out to celebrate and express itself in its own inimitable way. Around the time that Julius Erving and Allen Iverson were sharing a courtside hug, 76ers fans at the Wells Fargo Center were filing into the arena so they could boo Ben Simmons, a former member of their team, as he warmed up for a game in which he would not play.

The fans, at least, were out for payback, eager to share how they felt about Simmons, a one-time star who had spurned their team and effectively forced his way out last month. Now employed by the Nets, Simmons changed into casual clothing for his new team’s game against the 76ers on Thursday night and soon found a spot on the visitors’ bench. He had a great vantage point to enjoy a rout.

One game is not a referendum on two teams’ fortunes, or on a seismic trade that rattled the N.B.A. But what transpired in Philadelphia was jarring in all kinds of ways. The Nets were amazing. The 76ers were awful. And for two teams that could find themselves meeting in the postseason, the fallout could linger.

“It was lovely,” the Nets’ Kyrie Irving said.

“We’ve got a lot of work to do,” the 76ers’ Tobias Harris said.

As the Nets went about their business of plowing their way to a 129-100 win, a few narratives, some of them familiar, surfaced: Who would want to face the Nets in the first round of the playoffs? Has there even been a more dangerous team that has spent so many months teetering on mediocrity? And what are we supposed to make of the new-look 76ers, a team that has been vying for the top seed in the Eastern Conference, after that debacle?

“I don’t want to say they wanted to win any more than us,” said Doc Rivers, the coach of the 76ers. “But they played that way. It was clear. Every single loose ball. Every long rebound. They got to everything tonight. They blew up simple dribble handoffs that we run. They ran right through us.”

It sounded as if those dribble handoffs were going to haunt Rivers. He said he had counted nine instances when Nets defenders intercepted them. (The 76ers had a lot of lackluster dribble handoffs.)

A small thing, and correctable? Perhaps. The 76ers had been skating along quite nicely since the big trade last month, the one that sent Simmons to Brooklyn and James Harden to Philadelphia. In fact, entering Thursday, the 76ers had won all five games in which Harden had appeared in uniform for them, most of them by lopsided margins, including a 15-point victory over the Chicago Bulls on Monday. And Harden had been terrific, averaging 24.6 points and 12.4 assists while shooting 53.1 percent from the field, forming a fearsome tandem with Joel Embiid.

But Harden’s performance against the Nets — 3 of 17 from the field, 11 points, 4 turnovers — did little to remedy his reputation as a player who is prone to struggling in big games. He was also outshone by one of the other players who was included in last month’s trade: Seth Curry, who ought to be overlooked no more. Against the 76ers, he scored 24 points while helping to space the floor for Irving and Kevin Durant.

Afterward, Harden did his best to spin his night forward. Maybe, he said, the 76ers needed to get their butts kicked.

“Since I’ve been here, everything has been sweet,” he said. “We’ve been winning games. So tonight was good for us, and we get an opportunity to come down to reality, watch film and continue to get better.”

It should be noted that not everything is rainbows and puppy dogs for the Nets, who have lost 17 of their last 22 games. Simmons, who has not played since last season, is still working his way back into playing shape, and who knows how he will jell with the Nets once he returns. And Irving, who is unvaccinated, still cannot play in home games. Barring a change in public policy, that will remain the case in the postseason. But when Irving is available to play, look out. He scored 50 points against the Charlotte Hornets on Tuesday, and he and Durant combined for 47 on Thursday.

“Coming into the game,” Irving said, “I just told the guys, ‘Simplify it. Two baskets and a basketball. Don’t pay attention to what’s going on. No distractions. No fear. And let’s just live with the results.’ ”

Before the game, Rivers was asked if he thought the 76ers and the Nets constituted a rivalry. Not yet, he said. The Yankees and the Red Sox have a rivalry. Duke and North Carolina have a rivalry. Rivers even cited the rivalry between the 76ers and the Boston Celtics, one that dates back decades. Rivers recalled that when he was coaching the Celtics and lost an important game to the 76ers, Tommy Heinsohn, the former Celtics great who was working as one of the team’s television broadcasters at the time, “almost killed me.”

Still, the 76ers and the Nets are now connected in an odd way, having swapped disgruntled stars. They are also growing familiar with one other as title hopefuls in the same division. As for their becoming rivals?

“Let’s make it one,” Rivers said. “Both of us want the same thing, right? We have the exact same goal.”

For one night, at least, one team seemed closer to reaching that goal than the other.